Young leaves are wilted on this drought-stressed Pittosporum undulatum

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Drought tips for lanDscape managersThe following article is reprinted by permission from the California Center for Urban Horticulture website. (http://ccuh.ucdavis.edu) Some additions have been made to the original text.

reDuce irrigation

Provide only as much water as the landscape requires. Most landscapes are given too much water and can flourish on less. Over-irrigation can actually predispose plants to other problems.

• To learn more, see this page: Estimating Water Needs of Landscape Plants and Entire Landscapes.

• To find the water use of landscape plants in California, see this page: WUCOLS IV.

Prioritize plants During irrigation restrictions, select the highest value plants to receive the limited amounts of water available for irrigation. One way to determine this is to think about which plants can tolerate limited water and which are more easily replaced if allowed to die. Lower priority plants may also be removed from crowded areas to further conserve water.

Although they can be irrigated less frequently, trees should be prioritized, since they take longer to establish and will take more time to replace if allowed to die. Slow, deep soaking once or twice a month may be sufficient to keep them healthy. If they have been grown in a lawn, their roots may be shallow and they may require the more frequent twice-monthly irrigation.

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VOLUME 4, ISSUE 2

Expect some stress

Plants will respond to water stress in different ways but can recover. Recognize water stress symptoms to determine how long plants can go without irrigation [trees]. Adjust expectations of plant performance during drought. A helpful publication for lawns is Managing Turfgrasses During Drought.

Maximize Water efficiency

Optimize your irrigation system with regular system checks, including full audits. For a free guide, download this: Landscape Irrigation System Evaluation and Maintenance.

• Know what each valve controls: what kinds of emitters (sprinklers, drip, etc.), how many there are, and the plant types in each zone.

• Make repairs quickly: adjust sprinklers as necessary; replace plugged drip emitters, and repair leaks properly.

Low water plantings like this manzanita and fescue need half the water of turfgrass or less

2Green Notes

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• Change out older sprinklers to newer water efficient ones – check for rebates offered by your water purveyor. Replace spray heads with rotary stream heads (e.g. Rain Bird RN or R-VAN, Toro PRN, Hunter MP Rotator, Orbit Eco-Stream) that deliver water at lower pressure and flow rates.

• Switch to drip or subsurface irrigation where appropriate. Most shrub borders are better served by efficient in-line drip systems laid in a grid; over time regular spray heads become blocked by large shrubs and do not deliver water evenly to beds.

• Utilize technology such as smart controllers and soil moisture sensors (tensiometers). There may be rebates available from the client’s water purveyor to replace or install smart controllers.

• Schedule irrigation quantity and frequency to match the needs of the landscape- don’t just pick a random amount of time and set the timer. There are helpful publications and online resources to help you if you need it. Adjust the program in your irrigation controller at least monthly as the weather changes to better match plant needs.

• Water deeply and infrequently to discourage shallow rooting. Shallow-rooted plants are less tolerant of drought. The only way to

know if your water has reached the desired depth is with a shovel, long screwdriver, or soil probe. Check!

• Eliminate runoff by irrigating in cycles and replacing and/or adjusting sprinklers that irrigate hard surfaces. Understanding soil properties can help. The heavier the soil, the more slowly water will infiltrate.

• Avoid watering below the root zone. If soil is very sandy, you can easily apply water that moves below plant roots and is wasted. You will need to irrigate for shorter periods of time more frequently to keep water in the desired root zone (top 6-12” for grass; top 12’-24” for trees and shrubs).

• Manage irrigation for microclimates within your landscape. For instance, plants in shade can be irrigated far less frequently than those in full sun.

Pre-conDition lanDscapes for Drought survival

Slowly reduce irrigation volume if adjustments have not been made earlier in the season. Suddenly witholding all water can shock plants.

Contributing authors:

Dave Fujino, CCUH, UC Davis

Darren Haver, UC Cooperative Extension

Loren Oki, UC Cooperative Extension

Jennifer Tso, UC Davis

other Water-conserving tips

• Make sure all plants on a particular valve have similar water needs.• Promote soil health to improve infiltration: grasscycle, aerate turf, and use compost to improve

soil structure and slowly add nutrients. Cover exposed soil surfaces with mulch to reduce evaporation, prevent compaction, and suppress weeds which compete for water.

• During drought reduce or eliminate fertilizer to curb excessive tender growth.• In severe drought, prune back large, wilted plants to reduce water loss from plant leaves.

manage for salts

Shallow frequent irrigation with very hard or recycled water concentrates salts at the soil surface. If water is not yet restricted, water beyond the root zone to leach away salts at least once a month. This is especially important if the winter has been dry.

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14some truly loW-Water plants for the valley

These are just a few of the plants that will perform well on monthly summer water in clay loam soil, or every 2-3 weeks in sandy loam, provided water is applied to a depth of 18 inches. For at least the first year, be sure to water them regularly and deeply to establish a drought-tolerant root system. To search for more plants by category or name, visit WUCOLS IV. Plants for SHADE are noted.

Shrubs Arctostaphylos species and cultivars (manzanita)Berberis aquifolium and ‘Compacta’ (Oregon grape) SHADECallistemon species and cultivars (bottlebrush)Ceanothus species and cultivars (CA lilac)Daphne odora ‘Aureomarginata’ (winter daphne) SHADEFrangula californica and cultivars (coffeeberry)Heteromeles arbutifolia (toyon) SUN or SHADESalvia clevlandii and cultivarsSollya heterophylla (bluebell creeper) SHADE

Herbaceous Perennials/GrassesAchillea species and cultivarsAgastache species (mint hyssop)Elymus condensatus ‘Canyon Prince’ (wild rye)Festuca californica (California fescue) SHADEHellebore spp. and hybrids (Lenten rose) SHADEHeuchera spp. and hybrids (coral bells/alum root) SHADETulbaghia violacea (society garlic)Groundcovers Rosmarinus officinalis ‘Prostratus’ (creeping rosemary)Salvia spathacea (hummingbird sage) SHADETeucrium chamaedrys ‘Prostrata’ or ‘Nanum’ a border of Teucrium

Oregon grape in bloom

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4Green Notes

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Plant thisRosa ‘Korbin’ (Iceberg rose)This landscape rose is a handsome, disease-resistant, pest-tolerant shrub that blooms from spring until winter. The fragrant flowers fill the garden with their perfume and attract a variety of pollinators.It has been proven in trials to perform beautifully on about the half the water of a typical lawn. In clay-loam soils this means it will do well with only once or twice a month deep irrigation.Once or twice a summer you should remove the dead flower heads to keep it blooming. Then in mid-winter, remove all but 5-7 good canes, and cut these back to healthy buds about 2 feet high.This can be seen blooming from April through December in The Learning Landscape demonstration gardens at the Robert J. Cabral Agricultural Center, 2101 E. Earhart Ave., Stockton.

Reduce Pruning5

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contact us:Karrie ReidEnvironmental Horticulture AdvisorUC Cooperative ExtensionSan Joaquin County2101 E. Earhart Ave., Ste. 200Stockton, CA 95206-3949209-953-6109

skreid@ucanr.edu

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